A star of the Republican party, Christie for the past week has been dealing with a scandal since officials released e-mails showing a top aide calling for lane closures on the George Washington Bridge in evident retribution against the Democratic mayor of Fort Lee, New Jersey.

The governor’s office said it had retained the law firm of Gibson, Dunn & Crutcher LLP to help with an internal review and to cooperate with an investigation announced last week by U.S. Attorney for New Jersey Paul Fishman.

The outside attorneys will bring a “third-party perspective to the situation, and they will be a valuable asset as we move forward,” Christie spokesman Michael Drewniak said in the statement.

Randy Mastro will lead the outside legal team. During the 1990s, Mastro served as a deputy mayor to another moderate Republican who would go on to have presidential aspirations: former New York City Mayor Rudy Giuliani.

Christie, widely considered a top contender for the White House in 2016, said last week he would cooperate with the federal probe of the unexpected shutdown over four days in September of three local access lanes to the George Washington Bridge linking New Jersey and New York City.

E-mails released last week seemed to link two of Christie’s top aides to the decision to snarl traffic in Fort Lee in an effort to punish the town’s Democratic mayor for not supporting the governor’s re-election effort.

Christie has adamantly denied being part of the apparent scheme and fired his deputy chief of staff, Bridget Anne Kelly, and severed ties with former campaign manager Bill Stepien over their apparent orchestration of the lane closures.

New Jersey lawmakers are also expanding their probe of the scandal, which has become known as “Bridgegate.” Both houses of the state legislature scheduled special sessions on Thursday to empanel committees with subpoena power to investigate the closures and any further links to Christie’s office.

Christie said at a press conference last week that he was “blindsided” by revelations that Kelly, one of his closest advisers, had sent an e-mail in August saying: “Time for some traffic problems in Fort Lee.”

The man who received the e-mail, David Wildstein, a Christie appointee at the Port Authority of New York and New Jersey, which oversees operations at the bridge, responded: “Got it.”

Wildstein and his superior, Bill Baroni, also a Christie appointee at the Port Authority, both resigned late last year amid controversy over the closures.